Another Republican running for the USsSenate has angered voters, after telling a live television audience that when a woman becomes pregnant during a rape, "That's something God intended."

Richard Mourdock, Indiana denate candidate who has been locked in one of the country's most expensive and closely watched races, was asked during a debate on Tuesday whether abortion should be allowed in cases of rape or incest.

"I struggled with it myself for a long time, but I came to realise that life is that gift from God. And, I think, even when life begins in that horrible situation of rape, that it is something that God intended to happen," Mourdock said.

Mourdock became the second Republican senate candidate to find himself on the defensive over comments about rape and pregnancy.

Todd Akin, Missouri senate candidate, said in August that women's bodies had ways of preventing pregnancy in cases of what he called "legitimate rape".

Women voters are key to this year's presidential race, and Republican challenger Mitt Romney has been drawn into this latest issue.

Akin has repeatedly apologised but has refused to leave his race despite calls to do so by leaders of his own party, including Romney.

Romney distanced himself from Mourdock on Tuesday night, a day after a television ad featuring him supporting Mourdock began airing in Indiana.

"Gov Romney disagrees with Richard Mourdock's comments, and they do not reflect his views," Andrea Saul, Romney spokeswoman, said in an email to the Associated Press news agency.

'Spoke from the heart'

Mourdock said on Wednesday he stood by the controversial comments. He said that he "spoke from the heart" during the debate and that his comments had been "twisted" by people.

He apologised, however, for any misinterpretation of his statement.

"I abhor any kind of sexual violence," he said at a news conference on Wednesday. "I am absolutely confident that the God I worship abhors violence."

Mourdock explained after the debate that he did not believe God intended the rape but that God is the only one who can create life.

"Are you trying to suggest somehow that God pre-ordained rape? No, I don't think that," Mourdock said. "Anyone who would suggest that is just sick and twisted. No, that's not even close to what I said."

Mourdock has consistently opposed abortion, with the exception of cases where the mother's life is in danger.

Romney aides would not say whether the Republican presidential nominee would continue to support Mourdock's Senate bid.

Mourdock's comments shake Republicans as they try to gain a majority in the Senate. Republicans need to gain three seats, or four if President Barack Obama wins re-election.

Some seats that were predicted to remain or turn Republican have grown uncertain.